<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .fl{
            float:left;
            background-color: green;
            width: 100px;
            height:100px;
        }
        .main {
            height: 100px;
            background-color:pink;
            overflow: hidden;
        }
    </style>
</head>
<body>
    <!-- 1. 利用浮动进行两列式布局
    2. 左边元素利用了浮动，右边元素忽略左边元素，从最左侧开始排列
    3. 由此元素添加overflow:hidden属性，产生新的BFC
    4. 因为BFC规则的第五条，BFC区域和float不会重叠 -->
    <div class="parent">
        <div class="fl"></div>
        <div class="main">121212121212121212121212121212121212121212</div>
    </div>
</body>
</html>